Known in the art is a spark ignition type internal combustion engine provided with a variable compression ratio mechanism able to change a mechanical compression ratio and a variable valve timing mechanism able to control a closing timing of an intake valve, wherein the amount of intake air fed into a combustion chamber is mainly controlled by changing the closing timing of the intake valve, and the mechanical compression ratio at the time of engine low load operation is made higher compared with at the time of engine high load operation (for example, PLT 1).
In particular, since the expansion ratio has a greater effect on the theoretical heat efficiency than the actual compression ratio, in the spark ignition type internal combustion engine described in PLT 1, at the time of engine low load operation, the actual compression ratio is kept low while the mechanical compression ratio is made a high value, for example of 20 or more. Due to this, in the spark ignition type internal combustion engine described in PLT 1, the theoretical heat efficiency is made extremely high. Along with this, the fuel consumption is greatly improved.